The Nightline report revealed how close Johnson came to dying, and how much he struggled to get where he is today. Johnson can walk up stairs. He has limited movement with his right arm. Woodruff asked Johnson how many years he'll be improving. Johnson responded, "forever."

Johnson is up for re-election next year. Over the course of their interview sessions, Woodruff asked Johnson several times if he's running for re-election. Usually Johnson answered that he didn't know. Last week, Johnson was far more definite.

Johnson on stageMPR Photo/Cara Hetland

"I expect to run and to win," Johnson said.

That statement is causing some speculation on news blogs around the country. Johnson's press secretary issued a release saying a decision hasn't been made.

"It wasn't a definitive statement," said Bill Richardson, a political scientist at the University of South Dakota. "It was a statement you would expect from somebody who still has a fight with a body that has conspired against him, with a mind that's still the old Tim Johnson's mind."

Richardson said Johnson's public appearance bought him time to make a decision about his political future. He said the crowd was sympathetic and emotional, and will be more understanding.

Richardson said Johnson has proved to his constituents that he's a fighter and he has fight left in him. He said people in South Dakota look at Johnson differently now -- not sympathetically, but with patience and compassion.

"You might be able to consider him the new Teflon senator. It will be very hard for any prospective opponent to decide -- how do you campaign against THIS Senator Johnson?"

This Sen. Johnson, with slower speech and a wheelchair, promised his constituents, from all political parties, that he'll work hard, like he always has.

"The greatest honor in my life has been to stand by your side and fight for you in Washington. Never in my life have I been so grateful that you have been standing by my side as well," Johnson said.